The invention relates to a detecting device including sensing means for accurately detecting characteristics of a medium in proximity to said sensing means. Position is one such characteristic.
Prior art sensors used as proximity or position detectors for example are subject to various problems. A typical position detector is a mechanical limit switch. The contacts of such a switch create bounce which causes considerable difficulty in the switch circuit. Additional circuit elements are required to handle this problem which adds cost to the device. The switch contacts wear and the mechanical switch elements wear over a period of time causing a change in the mechanical point of switching with time. The use of mechanical switch elements makes it difficult to determine position within a high degree of accuracy due to the necessity of holding the movable mechanical parts in precise positions.
Some position detection devices have been developed which eliminate the use of the mechanical parts. However, these devices involve complex circuitry and do not attain the high degree of reliability which is sought by the user. Existing devices require balancing and "tweeking" of the circuit to the sensor thereby eliminating interchangeability of sensors without readjusting the circuit for proper operation with the new sensor. When such devices fail, there is no means to immediately detect the inoperability of the device.